Download Chapter 29 The Solar System

Our Solar System
•
BIG Idea:
• Using the laws of
motion and gravitation,
astronomers can
understand the orbits
and the properties of
the planets and other
objects in the solar
system.
I. Models of the Solar System
A. Geocentric (Earth-centered) model: the
Sun, stars, and planets revolve around the
Earth.
– Aristotle promoted
this Earth-centered model
B. Heliocentric (Sun-centered) model:
the Sun is the center of the universe
- Copernicus proposed this Sun-centered
model
Kepler’s Laws:
Explained planetary motion
mathematically.
1. The orbits of planets are
ELLIPSES (ovals) with the
SUN at one FOCUS.
• Because the planets’ orbits are
elliptical, they are not always the same
distances from the sun…
– Do you remember the word to describe
the point in our orbit when we are closest
to the Sun?
– Farthest away?
2. A planet must move more
RAPIDLY when it is CLOSE
to the sun and more
SLOWLY
when it is
FAR from
the sun.
3. Planets in LARGE orbits
take much LONGER to orbit
the sun than do planets in small
orbits.
• There are TWO types of
planets in our solar system…
• How were you taught to
remember them?
Planet Acronyms
• My Very Excellent Mother Just
Served Us Nachos
• My Very Excellent Mother Just
Served Us Noodles
• My Very Educated Mother Just
Served Us Nachos
II. The Inner Planets
(4 planets closest to the Sun)
• Terrestrial Planets: Earth-like
(rocky)
A. Mercury
• Closest to the Sun
• Shortest orbit of 88
days
• No atmosphere
•Heavily cratered
•Huge temperature
range 427ºC in
day, -173ºC at
night
Mariner 10 – visited the planet in 1974
and 1979
B. Venus
•Hot
surface:
(464ºC)
• Earth’s twin (size,
mass, density)
• Retrograde Rotation:
•Dense
clockwise (opposite
atmosphere
(96.5% CO2)
that of all other
planets)
•Orbital period: 224.65 days
•Slowest rotational period: 243 days
•Brightest planet viewed from Earth
•Pressure is 90xs that of Earth’s
•Clouds of sulfuric acid
•Trace amounts of water in atmosphere
Magellan Probe
C. Earth
•
•
•
•
•
Third planet from Sun
Orbital period of 365.24 days
Completes one full rotation in 23 hours 56 minutes
Fifth largest planet
Located between the Sun
and the Asteroid Belt
• One natural satellite: the
moon
Life on Earth is possible because…
• …of the Earth’s distance from the Sun
Temperature is warm enough for water to
exist as a liquid
Water occurs on Earth as a solid (ice), a
liquid, or a gas (water vapor)
The only known planet with the proper
combination of water, temperature, and
oxygen to support plant and animal life
Earth’s Atmosphere
D. Mars
•
•
•
•
•
Axis is tilted like Earth’s
Orbit = 687 Earth days
Rotation = 24 hours, 40 minutes
Very thin atmosphere (mostly CO2)
Olympus Mons – shield volcano
 Largest known volcano in
our solar system
 3X higher than Mt. Everest
Viking 1 – first found evidence
of water erosion
III. The Outer Planets
• Jovian Planets: Jupiter-like gas giants
A. Jupiter
• LARGEST planet
•
•
•
•
•
•
Fastest rotation: every 10 hours
Orbital period: 12 years
Mostly hydrogen and helium
More than 60 moons
Largest moon in our solar system: Ganymede
“Great Red Spot”: huge rotating storm
(about 3 times the size of Earth);
very cold (-260 degrees F)
• 100 lbs. on Earth = 264 lbs. on Jupiter
B. Saturn
•
•
•
•
LOWEST density
Average temperature: -176ºC
Orbital period = 29.5 years
Complex system of rings
(ice)
Cassini Spacecraft
C. Uranus
• Rotates horizontally
• The ‘tipped’ planet
• Orbital period = 84
years
• Faint, rocky rings
• Greenish color
• Methane atmosphere
• “Ice Giant”
Voyager 2
D. Neptune
• Orbital period = 164 years
• 11 known satellites (moons)
and possibly 4 rings
• Upper atmosphere composed of white
clouds of frozen methane (appear as bands
moving between equator and poles)
• “Great DARK Spot” violent swirling
masses of gas (like a hurricane) –
disappeared in 1994
• Solar system’s strongest winds – exceeding
1,000 km/hr
IV. Other Solar System Objects
A. Dwarf Planets:
•
•
•
•
orbit the Sun,
are not satellites (moons),
are nearly round in shape,
and have not cleared their orbits of
smaller debris.
1. Pluto
(now ‘asteroid #134340’)
• Late to be discovered (1930)
• Mostly frozen methane, rock,
and ice
• Demoted from planet
status to “dwarf planet”
in August 2006
Not always the furthest
planet from the sun
2. Ceres: largest body in
the Asteroid Belt
3. Eris:
•
•
largest known dwarf
planet
27% more massive
than Pluto
4. Makemake
5. Haumea
B. Small Solar System Bodies
1. Asteroids
• thousands orbiting
the Sun between
Mars and Jupiter
• rocky bodies
• vary in diameter
• pitted, irregular surfaces
Asteroid Belt
• between Mars and Jupiter
• remains of unformed planets
(planetesimals)
 meteoroid: small bits of rocks and metal left
by a comet or asteroid collision
 meteor: bright streak of light produced by
meteoroids burning up as they enter our
atmosphere
 meteorite: meteoroid (or part of one) that is
left after it hits the Earth
• Meteor Shower
“shooting stars”
• Meteorite: meteoroid that makes it
to Earth
• When large meteorites strike Earth,
they produce impact craters:
•
2. Comets
• small, icy bodies of rock, dust,
methane and ammonia
• orbit the Sun in long ellipses
1. Nucleus: small solid core, which is
made up of rocks, metals, and ice
2. Tail: gas and dust
In relation to the Sun, what do you
notice about the tails of the
comets?
• The tails always point AWAY from
the Sun!
• Their tails of gas and dust are
pushed away by radiation from the
Sun.